Temperature compensating voltage generator circuit

Description

[0001] The present invention relates to a temperature compensating voltage generator circuit, and more particularly to a temperature compensating voltage generator circuit used for the temperature compensation of electric circuits the electric characteristics of which can be controlled by a control voltage.

[0002] In general, the electric characteristic of an electric circuit such as the gain or oscillation frequency of an amplifier or an oscillator changes due to the change of the temperature of the surroundings and, therefore, such an electric circuit often comprises a means for temperature compensation. For example, as illustrated in Fig. 1, a control voltage such as a DC bias potential of an electric circuit CKT, such as an amplifier which is operated by an operating voltage V_cc, is produced by a control voltage generator circuit, i.e. temperature compensating voltage generator circuit consisting of resistors R1 and R2 and a negative coefficient temperature sensitive resistor S, and the control voltage is changed in accordance with the change of the ambient temperature so that the electric characteristic such as the gain of the electric circuit CKT is maintained constant.

[0003] Since the theoretical estimation of the temperature characteristics of the electric circuit CKT is generally difficult, the temperature characteristics are in practice measured by using the practical circuit device and the resistors R1 and R2 and the negative temperature coefficient temperature sensitive resistor S are selected. However, in many cases the temperature characteristics of the electrical circuit CKT do not show simple or linear curves, so that the conventional means cannot effect the substantially complete temperature compensation and it takes a long time to determine the characteristic of the temperature compensating voltage generator circuit. When the characteristics of the electrical circuit CKT have changed due to a variation in the ambient conditions, it is necessary to stop the operation of the electric circuit CKT in order to readjust the characteristic of the temperature compensating voltage generator circuit.

[0004] When it is necessary to effect complete temperature compensation, the characteristic of the electric circuit is measured at various temperatures and the control voltages, i.e. the temperature compensating voltages at the measured temperatures are determined so that the characteristic of the electric circuit is equalized. However, in the conventional temperature compensating voltage generator, it is impossible to adjust the value of the control voltage independently at various temperatures, so that the adjustment of the compensating voltage of the temperature compensating voltage generator circuit is very difficult. For example, when the compensating voltage is adjusted at another temperature after an adjustment of the compensating voltage at a base temperature, for example a normal temperature, the compensating voltage at the base temperature which was previously adjusted, changes.

[0005] Moreover, in the abovementioned conventional circuit, when the temperature characteristic of the control voltage for effecting temperature compensation cannot be approximated by a first order curve, it is very difficult to effect temperature compensation.

[0006] In the document Revue de Physique Appli- quee, volume 12, No. 3, March 1977 (Paris, FR) J. P. Troadec et al, "Measure simultanee d'une temperature moyenne et d'une difference de temperature centree sur cette moyenne. Application a I'enregistrement direct du pouvoir thermoelectrique en fonction de la temperature", pages 503-509, there is disclosed the principle of using a differential amplifier and a plurality of voltage dividers to combine effects from a plurality of circuits to obtain a compound signal with adjustable characteristics. It is also known from United States Patent Specification No: U.S. 3454903 to use an operational amplifier in a similar way with each circuit comprising a temperature sensitive circuit, the compound signal provided by the operational amplifier being a temperature compensating voltage.

[0007] It is an object of the present invention to provide an improved temperature compensating voltage generator circuit.

[0008] According to the present invention, there is provided a temperature compensating voltage generator for compensating temperature characteristics of an electric circuit whose electrical characteristic can be controlled by a control voltage comprising a plurality of voltage dividers, a plurality of temperature sensitive resistor circuits of different characteristics, and an operational amplifier the output of which provides a temperature compensating voltage, characterised in that the output voltages of all but one of the voltage dividers are adjustable and are provided to one input of the operational amplifier through said temperature sensitive circuits, the output voltage of the said one voltage divider is provided to the said input of the operational amplifier either directly or through a fixed resistor, and the other input of the operational amplifier is provided with a reference voltage through an additional voltage divider.

Brief description of the drawings

[0009] 

Fig. 1 is a block circuit diagram illustrating an electric circuit comprising a conventional temperature compensating circuit;

Fig. 2 is a circuit diagram illustrating a temperature compensating voltage generator circuit which is a first embodiment of the present invention;

Fig. 3 is a circuit diagram illustrating a voltage regulator circuit incorporating the temperature compensating voltage generator circuit of Fig. 2;

Fig. 4 is a circuit diagram illustrating a temperature compensating voltage generator circuit which is a second embodiment of the present invention;

Fig. 5 is a block circuit diagram illustrating the use of a temperature compensating voltage generator circuit according to the present invention in a transmitter system; and

Fig. 6 is a block circuit diagram illustrating the use of a temperature compensating voltage generator circuit according to the present invention in an amplifier circuit.

Description of the preferred embodiments

[0010] With referenceto the attached drawings, the present invention will now be explained.

[0011] Fig. 2 is a circuit diagram illustrating a temperature compensating voltage generator circuit according to the present invention. The circuit of Fig. 2 comprises adjustable or variable resistors RV191 through RV193 constituting voltage dividers whose voltage division ratios are adjustable, a NTC resistor S191, a PTC resistor P191, resistors R191 through R194 and an operational amplifier OPA191. In Fig. 2 OUT designates an output terminal of the control voltage and +V_cc designates a power supply voltage. In the circuit of Fig. 2, a constant voltage from a voltage divider circuit which consists of the resistors R192 and R193 and which divides the power supply voltage +V_cc is applied to the non-inverted input terminal of the operational amplifier OPA191. The inverted input terminal of the operational amplifier OPA191 receives the voltages adjusted by the adjustable resistors RV191, RV192 and RV193 through the NTC resistor S191, the resistor R191 and the PTC resistor P191 respectively, that is, the adjusted voltages are added by the adder circuit which comprises the NTC resistor S191, the resistor R191, the PTC resistor P191, the feedback resistor R194 and the operational amplifier OPA191 and which adds the adjusted voltages under the gains corresponding to the ratio of the resistance of the NTC resistor S191, the resistor R191 and the PTC resistor P191 to the feedback resistor R194.

[0012] At a base temperature, the resistance of the NTC resistor S191 and the PTC resistor P191 is larger than that of the resistor R191, and thus the gain of the voltage adjusted by the adjustable resistor RV192 is larger than that of each of the voltages from the adjustable resistors RV191 and RV193. Therefore, at the base temperature, the control voltage V can be adjusted by the adjustable resistor RV192.

[0013] At a low temperature which is lower than the base temperature, the resistance of the PTC resistor P191 becomes smaller so that the gain of the voltage adjusted by the adjustable resistor RV193 becomes large and, therefore, the control voltage V_G at the low temperature can be adjusted by the adjustable resistor R193.

[0014] At a high temperature which is higher than the base temperature, the resistance of the NTC resistor S191 becomes smaller so that the gain of the voltage adjusted by the adjustable resistor RV191 becomes large and, therefore, the control voltage V_G at the high temperature can be adjusted by the adjustable resistor R191. If the control voltage is adjusted at the base temperature, the adjustable range of the control voltage in a predetermined temperature range is shifted. Fig. 3 illustrates a voltage regulator system comprising the control voltage generator circuit of Fig. 2. In Fig. 3, a voltage regulator circuit CKT2 receives an input voltage V_in and outputs a stabilized output voltage V_out. The regulating characteristic of the voltage regulator circuit CKT2 varies in accordance with the change of the ambient temperature and thus the potential of the output voltage V_out changes according to the variation of the ambient temperature. In order to gain the output voltage V_out having a constant potential, the control voltage, i.e. temperature compensating voltage V_a is applied from the control voltage generator circuit CONT2 to the voltage regulator circuit CKT2. The control voltage V_G is, for example, added to the error voltage of the voltage regulator circuit CKT2 detected from the output voltage V_out and a reference voltage not shown in the drawing.

[0015] Fig. 4 is a circuit diagram illustrating a second temperature compensating voltage generator circuit in accordance with the present invention. In Fig. 4, the same parts as appear in Fig. 2 are designated by the same reference symbols. In Fig. 4, RV221 is an adjustable resistor and R221 and R222 are resistors. At the base temperature, the control voltage V_a is adjusted by the adjustable resistor RV221, and the control voltage V_G is proportional to the difference between the adjusted voltage from the adjustable resistor RV221 and the voltage from the voltage divider circuit consisting of the resistors R221 and R222. At a low temperature, the resistance of the PTC resistor P191 becomes smaller and the voltage adjusted by the adjustable resistor RV193 is mainly added to the voltage at the base temperature. At a high temperature, the resistance of the NTC resistor S191 becomes smaller and the voltage adjusted by the adjustable resistor RV191 is mainly added to the voltage at the base temperature. Therefore, after the adjustment of the control voltage V_G by the adjustable resistor RV221, the control voltages at the low and the high temperatures can be adjusted independently by the adjustable resistors RV193 and RV191.

[0016] Fig. 5 is a block circuit diagram illustrating a transmitter system which includes a control voltage generator according to the present invention. The transmitter system of Fig. 5 comprises an intermediate frequency amplifier AMP1, a voltage controlled attenuator ATT, a mixer MIX, a local oscillator LOS, a band pass filter BPF, a transmitter amplifier AMP2 and a temperature compensating voltage generator CONT3 in which the control voltage can be adjusted independently at every adjusting temperature. In order to maintain the output signal level at a constant value, the conventional transmitter system used an automatic level control circuit (ALC) including a feedback loop as shown by the dotted line in Fig. 5 but did not contain the control voltage generator circuit CONT3. In such a conventional transmitter system, it was necessary to adjust the loop gain precisely so that the self-oscillation of the system did not occur and thus the design, manufacturing and adjusting of the circuit was difficult. In the transmitter system according to the present invention, the control voltage V_G is applied to the voltage controlled attenuator ATT from the control voltage generator circuit CONT 3 in order to compensate the gain-temperature characteristic of the transmitter amplifier AMP2 and to obtain a constant transmitting level. In the system according to the present invention, it is possible to omit the feedback loop contained in the conventional system and, therefore, it is possible to make up a stable transmitter system. In the transmitter system of Fig. 5, it is possible to use any one of the temperature compensating voltage generator circuits mentioned above.

[0017] Fig. 6 is a block circuit diagram illustrating an amplifier circuit which includes a control voltage generator circuit CONT4 according to the present invention in order to stabilize the gain thereof. The circuit of Fig. 6 comprises impedance matching circuits MT1 and MT2 disposed on the sides of the input terminal IN and the output terminal OUT, a field effect transistor FQ, the control voltage generator circuit CONT4 and two inductors L₁ and L₂. The control voltage V_G is supplied to the gate electrode of the field effect transistor FQ as a DC bias voltage from the control voltage generator circuit CONT4. The control voltage generator circuit CONT4 generates the bias voltage which compensates for the gain-temperature characteristic of the field effect transistor FQ so that the gain of the amplifier circuit does not change even when the ambient temperature has changed. In the amplifier circuit of Fig. 6, it is possible to use any one of the temperature compensating voltage generator circuits mentioned above.

Claims

1. A temperature compensating voltage generator for compensating temperature characteristic of an electric circuit whose electrical characteristic can be controlled by a control voltage comprising a plurality of voltage dividers (RV191, RV192, RV193; R221, R222), a plurality of temperature sensitive resistor circuits (S191, P191) of different characteristics, and an operational amplifier (OPA) the output of which provides a temperature compensating voltage, characterised in that the output voltages of all but one of the voltage dividers (RV191, RV193) are adjustable and are provided to one input of the operational amplifier through said temperature sensitive circuits, the output voltage of the said one voltage divider (RV192, R221, R222) is provided to the said input of the operational amplifier either directly or through a fixed resistor (R191), and the other input of the operational amplifier is provided with a reference voltage through an additional voltage divider (R192, R193; RV221).

2. A temperature compensating voltage generator as claimed in claim 1, wherein said one voltage divider includes an adjustable resistor (RV192) from which an adjustable output voltage is provided, and a resistor circuit (R191) which supplies said output voltage from said adjustable resistor to said one input of the operational amplifier.

3. A temperature compensating voltage generator as claimed in claim 1, wherein said one voltage divider consists of fixed resistors (R221, R222) from which an output voltage is supplied to said one input of said operational amplifier, and said additional voltage divider includes an adjustable resistor (R221) from which an adjustable output voltage is supplied to said other input of the operational amplifier.

Ansprüche

1. Spannungsgenerator mit Temperaturekompensation, zur Kompensation von Temperaturcharakteristiken einer elektrischen Schaltung, deren elektrische Charakteristik durch eine neutrale Spannung gesteuert werden kann, mit einer Vielzahl von Spannungsteilern (RV191, RV192, RV193; R221, R222), einer Vielzahl von temperaturempfindlichen Widerstandsschaltungen (S191, P191), mit verschiedenen Charackteristiken, und einem Operationsverstärker (OPA), dessen Ausgang eine Temperaturekompensationsspannung liefert, dadurch gekennzeichnet, daß die Ausgangsspannungen von allen außer einem der Spannungsteiler (RV191, RV193) einstellbar sind und zu einem Eingang des Operationsverstärkers durch die genannten temperaturempfindlichen Schaltungen geliefert werden, die Ausgangsspannung des genannten einen Spannungsteilers (RV192, R221, R222) an den genannten Eingang des Operationsverstärkers entweder direkt oder über einen festen Widerstand (R191) geliefert wird, und der andere Eingang des Operationsverstärkers über einen zusätzlichen Spannungsteiler (R192, R193; RV221) mit einer Referenzspannung versehen wird.

2. Spannungsgenerator mit Temperaturkompensation nach Anspruch 1, bei dem der genannte eine Spannungteiler einen einstellbaren Widerstand (RV192) umfaßt, von dem eine einstellbare Ausgangsspannung geliefert wird, und eine Widerstandsschaltung (R191 die die genannte Ausgangsspannung von dem einstellbaren Widerstand an den genannten einen Eingang des Operationsverstärkers liefert.

3. Spannungsgenerator mit Temperaturkompensation nach Anspruch 1, bei dem der genannte eine Spannungsteiler aus festen Widerständen (R221, R222) besteht, von denen eine Ausgangsspannung zu dem genannten einen Eingang des Operationsverstärkers geliefert wird, und der genannte zusätzliche Spannungsteiler einen einstellbaren Widerstand (R221) umfaßt, von dem eine einstellbare Ausgangsspannung zu dem anderen Eingang des Operationsverstärkers geliefert wird.

Revendications

1. Générateur de tension de compensation en température, servant à compenser les caractéristiques de température d'un circuit électrique dont la caractéristique électrique peut être commandée par une tension de commande, comprenant plusieurs diviseurs de tension (RV191, RV192, RV193; R221, R222), plusieurs circuits résistants sensibles à la température (S191, P191) de caractéristiques différentes, et un amplificateur opérationnel (OPA) dont la sortie fournit une tension de compensation en température, caractérisé en ce que les tensions de sortie de tous les diviseurs de tension (RV191, RV193) sauf un sont adjustables et sont fournis à une première entrée de l'amplificateur opérationnel via lesdits circuits sensibles à la température, la tension de sortie dudit diviseur de tension particulier (RV192, R221, R222) est fournie à ladite entrée de l'amplificateur opérationnel soit directement, soit par l'intermédiaire d'une résistance fixe (R191), et l'autre entrée de l'amplificateur opérationnel reçoit une tension de référence via un diviseur de tension supplémentaire (R192, R193; RV221).

2. Générateur de tension de compensation en température selon la revendication 1, où ledit diviseur de tension particulier comporte une résistance ajustable (RV192) duquel est produite une tension de sortie ajustable, et un circuit résistant (R191) qui délivre ladite tension de sortie de ladite résistance ajustable à ladite première entrée de l'amplificateur opérationnel.

3. Générateur de tension de compensation en température selon la revendication 1 où ledit diviseur de tension particulier est constitué de résistances fixes (R221, R222) desquelles une tension de sortie est délivrée à ladite première entrée dudit amplificateur opérationnel, et ledit diviseur de tension supplémentaire comporte une résistance ajustable (R221) de laquelle une tension de sortie ajustable est délivrée à ladite autre entrée de l'amplificateur opérationnel.

Drawing